Ecological Impact of Enhance Solar Ultraviolet Radiation on Phytoplankton at High Latitudes in the Arctic

点击翻译按钮获取中文摘要

9907692Holm-HansenRecent data shows that ozone concentrations in the stratosphere over the Northern Hemisphere during the spring period (March-May) are decreasing each succeeding year, continuing the decline that has been documented during the past decade. The magnitude of the depletion in atmospheric ozone is maximal at the higher latitudes in the Arctic, with progressively less depletion at lower latitudes. Depletion of this protective layer of ozone results in enhancing UV-B radiation (280-320 nm), with the influence of these shorter UV wavelengths incident upon the earth increasing exponentially with progressive loss of ozone. As the photons in the UV-B spectral region are highly energetic and their wavelengths overlap the absorption spectrum of many important cellular components (e.g., DNA), this enhanced UV-B radiation resulting from ozone depletion represents a significant threat to any living organism which is exposed to solar radiation. In this proposal we are concerned with the impact of solar UVR on Arctic marine phytoplankton, which constitute the base of the entire food web in the marine ecosystem.The project will be based at the Marine Biological Station of the University of Tromso, Norway, which is located at approximately 70 N and hence represents a high-latitude Arctic environment, but will also include ship-board studies in the Lofoten Islands and close to the ice edge in the northern Barents Sea. All experimental work will use either natural phytoplankton assemblages or unialgal phytoplankton cultures of ecologically relevant species in the Arctic food web. Both in situ incubations and temperature-controlled incubators with appropriate optical filters will be used to determine the impact of enhanced UV-B radiation (when column ozone values are low), 'normal' UV-B radiation, and UV-A radiation (320-400 nm) on structural damage to the genetic material in cells (DNA), on the loss of primary production, and on possible changes in species composition of the phytoplankton assemblages. Ancillary data will include the relationship between the magnitude of UV-induced cellular damage and the influence and total dose of UVR experienced by cells. Specific experiments will also determine whether or not the UV-induced cellular damage is reversible in time, and also the extent to which cells can mitigate the adverse effects of solar UVR by synthesis of UV-screening compounds. These studies will be supported by simultaneous measurements of relevant environmental factors, including incident spectral UVR and visible solar radiation with depth in the water column, and stability of the upper water column.The studies will be done in cooperation with personnel from the University of Tromso, who are also engaged in long-term monitoring of incident solar UVR in northern Norway. Students from both the USA and Norway will be active participants in the field work and in analysis of the data. The results from this cooperative project should provide a good data base to better our understanding of the possible impact of enhanced solar UVR on the floristic composition of the natural phytoplankton assemblages as well as on the rate of primary production. Such data will be important inputs to future modeling efforts to estimate the impact of progressive depletion of atmospheric ozone over the Arctic on the food resources available to higher trophic levels. As important fishery resources are located throughout the Arctic regions, such knowledge is also of importance in regard to economic and societal concerns.